1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, a light source device of a liquid crystal display device capable of minimizing leakage of power.
2. Description of the Related Art
As compared to Cathode Ray Tube (CRT) displays, liquid crystal display devices are lighter in weight, smaller in size, and provide full color and high resolution. As a result, many users prefer a liquid crystal display device over a CRT, for example, for use as a monitor of a computer or a household television that is hung on a wall, and the like.
Generally, when an electric field or an electric charge is applied to liquid crystal molecules, the liquid crystals become twisted, untwisted, or straightened in a predictable manner depending on the level of electric charge applied. The changing molecule pattern in the liquid crystals can be used to alter the optical characteristics of light passing through the crystals, such as blocking, passing, or partially passing the light. Therefore, the liquid crystal display device can display variations in images by controlling the liquid crystal cells.
FIG. 1 is an exploded perspective view showing a conventional liquid crystal display device and FIG. 2 shows the constructions of a lamp adapted to a lamp unit shown in FIG. 1.
Referring to FIG. 1, the liquid crystal display device 100 has a liquid crystal display module 130 for displaying an image when image signals are applied thereto and a front case 110 and a rear case 120 for receiving the liquid crystal display module 130. The liquid crystal display module 130 includes a display unit 170 having a liquid crystal display panel 171 for displaying the image and a backlight assembly 150 for providing light to the display unit 170.
The display unit 170 includes the liquid crystal display panel 171, a data printed circuit board 176, a gate printed circuit board 175, a data tape carrier package 178 and a gate tape carrier package 174.
The liquid crystal display panel 171 includes a thin film transistor substrate 172 and a color filter substrate 173.
The thin film transistor substrate 172 is a transparent glass substrate on which thin film transistors are formed in a matrix. Data lines are connected to source terminals and gate lines are connected to gate terminals of the thin film transistors. Furthermore, pixel electrodes made of transparent and conductive material, such as Indium Tin Oxide (ITO), are connected to drain terminals of the thin film transistors.
The color filter substrate 173, disposed against the thin film transistor substrate 172, provides color to the image viewed. The color filter substrate 173 has red, green, and blue (RGB) pixels, typically formed by a thin film process, to present desired colors when light passes through the color filter substrate 173. A surface of the color filter substrate 173 is covered with common electrodes made of ITO.
The thin film transistors of the thin film transistor substrate 172 correspond to the pixels of the display. They are selectively turned on and off to apply desired voltages to corresponding liquid crystals to change their orientations to pass or block the passage of light.
Control signals such as driving signals and timing signals are applied to the gate lines and data lines of the thin film transistors to control the amount of voltage applied at specified times to the liquid crystals in the liquid crystal display panel 171 to control the level of brightness affecting each pixel.
Image signals representing images to be displayed are received at the data printed circuit board 176 and the gate printed circuit board 175, which apply driving signals to the data lines and the gate lines of the TFT substrate 172 in liquid crystal display panel 171. The data printed circuit board 176 is connected to the data tape carrier package 178 for controlling the data line and the gate printed circuit board 175 is connected to the gate tape carrier package 174 for controlling the gate line in the liquid crystal display panel 171. A source portion is formed on the data printed circuit board 176 to receive the image signals from an information process device such as a computer, etc. and then to provide a data driving signal to the data line of the liquid crystal display panel 171. A gate portion is formed on the gate printed circuit board 175 to provide a gate driving signal for the gate line of the liquid crystal display panel 171. That is, the data printed circuit board 176 and the gate printed circuit board 175 generate the gate driving signal and the data signal for driving the liquid crystal display device and the plural timing signals for applying the gate driving signal and the data signal at a proper time, so as to apply the gate driving signal through the gate tape carrier package 174 to the gate line of the liquid crystal display panel 171 and the data signal through the data tape carrier package 178 to the data line of the liquid crystal display panel 171.
The backlight assembly 150 is disposed under the display unit 170 to supply light to the display unit 170 uniformly. The backlight assembly 150 includes lamp units 161 and 162 as light source. They are disposed at two ends of the liquid crystal display module 130. A light guide plate 152 guides the light to the display unit 170. A plurality of optical sheets 153 act to redirect and scatter evenly the light emitted from the light guide plate 152. A reflective plate 154 disposed under the light guide plate 152 reflects the light leaked from the light guide plate 152 toward the display unit 170.
The display unit 170 and the backlight assembly 150 are received in a mold frame 132, which is provided with a top chassis 140 for preventing the display unit 170 from separating from the mold frame 132.
Meanwhile, the liquid crystal display device has a bottom chassis 133 for shielding the display unit from electromagnetic waves. The bottom chassis 133 contains a printed circuit board (not shown, referred to as an inverter) including an inverter circuit to supply electricity to lamps of the lamp units 161 and 162.
The front case 110 is combined with the rear case 120 so that the mold frame 132 is placed between the front case 110 and the rear case 120, when the assembly of the liquid crystal display device is complete.
Referring to FIG. 2, the lamp units 161 and 162 respectively include a cold cathode tube 161a as a lamp, first and second power supply lines 163 and 164 for providing electric bias to the cold cathode tube 161a. Lamp holders 161b and 161c are used for positioning the cold cathode tube 161a. The first power supply line 163 applies a high voltage to the cold cathode tube 161a and the second power supply line 164 applies a low voltage to the cold cathode tube 161a. The first and second power lines 163 and 164 are connected to a connector 165 to receive an electric power source.
A plurality of lamps can be provided to each lamp unit of the liquid crystal display device, based on the size of the liquid crystal display device. If each of the lamp units 161 and 162 has two lamps, the number of power supply lines must be increased two times. That is, when there are two lamps disposed at each of two sides of the light guide plate 152, the power supply lines extending from each of the lamp units 161 and 162 respectively have two high voltage power supply lines 163 and 163a and two low voltage power supply lines 164 and 164a, as shown in FIG. 3.
The low voltage power supply lines and the high voltage power supply lines connected to both ends of each lamp are connected to a corresponding connector. The connector is connected with a connector of the inverter (not shown) mounted on a rear portion of the mold frame 132 to receive the power source. A shrinkable tube 167 wraps portions of the power supply lines 163, 163a, 164 and 164a extending out of the lamp units so that the power supply lines 163, 163a, 164 and 164a are prevented from interfering the assembly of the liquid crystal display device. From use of the shrinkable tube 167, the high voltage power supply lines 163 and 163a and the low voltage power supply lines 164 and 164a come in close contact with one another, as shown in FIG. 4, causing several problems. For example, power is leaked from the power supply lines due to coupling. That is, the power needed to operate the lamps needs to be increased. When power applied to the lamps is increased, the lamps tend to flicker. And, the overall consumption of power in using the liquid crystal display device increases due to the above-mentioned problems. Further, the above problems are more apparent when the liquid crystal display device is used in a low temperature environment, requiring a higher starting voltage and electric current.
The present invention solves the aforementioned problems, and accordingly it is the object of the present invention to provide a light source device capable of minimizing leakage of power provided to a lamp for generating light in a liquid crystal display device.
To achieve the above object, a light source device for use in a liquid crystal display device according to the present invention comprises: a light generating section for generating light; a power supply section for supplying power to the light generating section and a plurality of power supply lines for supplying the power source to the light generating section, which electrically connects the power supply section to the light generating section. Members for preventing leakage of power are formed on the power supply lines to prevent the power source provided from the light generating section from being leaked from the plurality of the power supply lines, which is mounted around the power supply lines. Preferably, these members include shrinkable tubes for wrapping the power supply lines.
According to a second aspect of the present invention, a liquid crystal display device according to the present invention comprises: a light generating section for generating light; a light guide plate for guiding the light to an image displaying section for displaying an image; a receptacle for receiving the light generating section and the light guide plate; and a power supply section for supplying a power supply to the light generating section, which is mounted in the receptacle. The light generating section receives the power source through a plurality of power supply lines connecting the power supply section to the light generating section. Members for reducing leakage of power are formed on the power supply lines to minimize or prevent the power provided to the light generating section from being leaked from the power supply lines.
The members for preventing the leakage of the power source are respectively coated on each power supply line so that the power supply lines are spaced apart from one another and each power supply line is a first power supply line for supplying a higher potential voltage to the light generating section and a second power supply line for supplying a lower potential voltage to the light generating section.
The plurality of the power supply lines includes at least two first power supply lines for supplying a high voltage to the light generating section and at least two second power supply lines for supplying a low voltage to the light generating section, and the two first power supply lines are respectively coated with the members for reducing the leakage of power to be spaced apart from each other and the two second power supply lines are together coated with the other members for minimizing the leakage of power.
The liquid crystal display device further comprises members for fixing the power supply lines to the receptacle to prevent separation of the power supply lines from the receptacle while guiding the power supply lines having the members for reducing leakage of power to the power supply section, which is formed on the receptacle. The members for reducing the leakage of power has connection members formed at a predetermined portion to connect the power supply lines to the fixing members.
According to the light source device and the liquid crystal display device of the present invention, the two first power supply lines for applying the higher potential voltage are spaced at a predetermined distance from each other. Accordingly, it is possible to reduce consumption of a power when a lamp is started and when the lamp is operating.
A light source device for a liquid crystal display device is also provided which includes: light generating means for generating light; power supply means for supplying power to the light generating means; a plurality of power supply lines for supplying power from the power supply means to the light generating means; and a shrinkable tube wrapped around the power supply lines for reducing power from being leaked from the plurality of the power supply lines.
According to an aspect of the present invention, the power supply lines include at least a first line for carrying a higher potential voltage and at least a second line for carrying a lower potential voltage, the first line being coated by material having a higher dielectric constant than material coating the second line.